The present invention relates to a circular waveguide polarizer to be used mainly in VHF band, UHF band, microwave band, and millimeter wave band.
FIG. 1 is a schematic configuration diagram of a conventional circular waveguide polarizer described, for example, in Proc. of The Institute of Electronics and Communication Engineers (published in September 1980, Vol. 63-B, No. 9, pp. 908-915). In the figure, reference numeral 1 denotes a circular waveguide, reference numeral 2 denotes a plurality of metallic posts inserted into the circular waveguide 1 through a side wall of the waveguide in pairs with respect to an axis C1 of the waveguide and arranged at predetermined certain intervals along the direction of the pipe axis C1 of the waveguide 1, and reference numeral P1 and P2 denote an input end and an output end, respectively. FIG. 2 is an explanatory diagram showing a conventional electromagnetic field distribution of a horizontally polarized wave and a vertically polarized wave.
The operation of the conventional circular waveguide polarizer will now be described.
It is here assumed that a linearly polarized wave in a frequency band f capable of being propagated through the circular waveguide 1 is propagated in a fundamental transmission mode (TE11 mode) through the circular waveguide 1 and is incident from the input end P1 in a 45xc2x0 inclined state of its polarization plane from an insertion plane of the metallic posts 2 as shown in FIG. 1. At this time, the incident linearly polarized wave can be regarded as being a combined wave of a linearly polarized wave perpendicular to the insertion surfaces of the metallic posts 2 and a linearly polarized wave horizontal to the insertion plane of the metallic posts 2, both having been incident in phase. Polarization components perpendicular to the insertion plane of the metallic posts 2, as shown on the right-hand side in FIG. 2, pass through the circular waveguide 1 with little influence from the metallic posts 2 and are outputted from the output end P2 due to the fact that an electric field intersects the metallic posts perpendicularly. On the other hand, the passing phase of polarization components horizontal to the insertion plane of the metallic posts 2, as shown on the left-hand side in FIG. 2, is delayed due to the fact that the metallic posts 2 serve as a capacitive susceptance since a magnetic field intersects the metallic posts 2 perpendicularly.
Thus, in the circular waveguide polarizer shown in FIG. 1, the metallic posts 2 act as a capacitive susceptance for the polarization component which is horizontal to the insertion plane. Therefore, the number, spacing and insertion length of the metallic posts 2 are appropriately designed so that a passing phase difference between the polarization component outputted from the output end P2 and perpendicular to the insertion plane of the metallic posts 2 on the one hand and the polarization component outputted from the output end P2 and horizontal to the insertion plane of the metallic posts 2 on the other hand is 90xc2x0. Thus, there is obtained a circularly polarized wave as a combined wave of both polarization components outputted from the output end P2. Namely, the linearly polarized wave incident from the input end P1 is outputted as a circularly polarized wave from the output end P2.
In the conventional circular waveguide polarizer constructed as above, since the metallic posts 2 are projected into the circular waveguide 1, disturbance is imparted to a section with a dense electric field distribution within the circular waveguide 1, allowing a phase delay to occur. Thus, the phase delay quantity or the reflection quantity vary greatly with a delicate change in insertion quantity of the metallic posts 2 into the circular waveguide 1. Therefore, the adjustment to obtain a desired passing phase characteristic or a reflection amplitude characteristic requires much time and there has been the problem that mass production and cost reductions are difficult.
Moreover, since the metallic posts 2 are projected to a section with a dense electric field distribution within the circular waveguide 1, there has been the problem that electric power resistance and low loss characteristic required of the circular waveguide polarizer are impaired.
The present invention has been accomplished for solving the above-mentioned problems and it is an object of the present invention to provide a high-performance low-cost circular waveguide polarizer.
According to the present invention, a circular waveguide polarizer is provided with side grooves arranged in a side wall of a circular waveguide.
Therefore, by appropriately designing the number, spacing, radial depth, circumferential width, length in a pipe axis direction, and the like of such side grooves, it is possible to delay a passing phase of a polarization component perpendicular to the installation plane of the side grooves by 90xc2x0 relative to a passing phase of a polarization component horizontal to the side groove installation plane. Thus, there is obtained an advantageous effect such that there can be realized a circular waveguide polarizer in which a linearly polarized wave incident from an input end is outputted as a circularly polarized wave from an output end.
Moreover, the side grooves are formed in the side wall of the circular waveguide and disturbance is imparted to a section with a coarse electromagnetic field distribution in a transmission mode (e.g., circular waveguide TE11 mode) to give a phase delay. Therefore, the amount of phase delay does not vary largely even with a delicate change in the width, depth and length of each side groove. That is, the deterioration in characteristics caused by a machining error for example is small and it becomes possible to effect mass production and the reduction of cost.
Further, since metallic projections such as metallic posts are not arranged in the circular waveguide, the circular waveguide polarizer has superior characteristics with respect to electric power resistance and loss.
In the circular waveguide polarizer according to the present invention, first to nth side grooves may be formed in a side wall of a circular waveguide, the side grooves are arranged along the pipe axis direction so as to be symmetrical with respect to a plane which divides the circular waveguide right and left into two.
With this arrangement, the circular waveguide polarizer displays improved reflection matching.
In the circular wave polarizer according to the present invention, first to nth side grooves may be formed in the side wall of the circular waveguide along the pipe axis direction so as to be symmetric with respect to a plane which divides the circular waveguide right and left into two, and further, n+1th to 2nth side grooves may be formed in positions opposed to the first to nth side grooves with respect to the axis of the circular waveguide.
With this arrangement, it is possible to suppress the generation of higher-order modes, and the circular waveguide polarizer can operate with improved characteristics over a wide band.
In the circular waveguide polarizer according to the present invention, a first side groove may be formed in the side wall of the circular waveguide and a second side groove may be formed in a position opposed to the first side groove with respect to the axis of the circular waveguide.
With this arrangement, it is possible to suppress the generation of higher-order modes and there is obtained a large phase delay at a short pipe axis length, so that the circular waveguide polarizer can be downsized and can operate with improved characteristics over a wide band.
In the circular waveguide polarizer according to the present invention, a radial depth of each of the first and second side grooves may be gently varied in the pipe axis direction.
With this arrangement, it is possible to suppress the generation of higher-order modes and there is obtained a large phase delay at a short pipe axis length, so that the circular waveguide polarizer can be downsized and can operate with improved characteristics over a wide band.
In the circular waveguide polarizer according to the present invention, a radial depth of each of the first and second side grooves may be varied stepwise in the pipe axis direction.
With this arrangement, since machining processes is facilitated, the circular waveguide polarizer can be mass-produced and the cost thereof can be reduced.
In the circular waveguide polarizer according to the present invention, the side grooves may be rectangular in sectional shape which is defined by the pipe axis direction and the circumferential direction.
As a result, since machining becomes easier, the circular waveguide polarizer can be mass-produced and reduced in cost.
In the circular waveguide polarizer according to the present invention, the side grooves may be semicircular at both ends in sectional shape which is defined by the pipe axis direction and the circumferential direction.
As a result, it becomes easier to effect machining and the circular waveguide polarizer can be mass-produced and reduced in cost.
In the circular waveguide polarizer according to the present invention, the side grooves may be rectangular in section which is defined by the radial direction and the circumferential direction.
As a result, it becomes easier to effect machining and the circular waveguide polarizer can be mass-produced and reduced in cost.
In the circular waveguide polarizer according to the present invention, the side grooves may be semicircular in section which is defined by the radial direction and the circumferential direction.
As a result, it becomes easier to effect machining and the circular waveguide polarizer can be mass-produced and reduced in cost.
In the circular waveguide polarizer according to the present invention, the side grooves may be sectorial in section which is defined by the radial direction and the circumferential direction.
As a result, a large phase delay can be obtained while keeping small the outermost diameter of the circular waveguide polarizer, so that the circular waveguide polarizer can be made smaller in size.
In the circular waveguide polarizer according to the present invention, a dielectric material may be disposed within each side groove.
As a result, the volume of each side groove with respect to the electromagnetic field becomes larger equivalently, and there is obtained a large phase delay in the side grooves of a small physical size, so that the circular waveguide polarizer can be made smaller in size.
According to the present invention, a circular waveguide polarizer comprises: first to mth circular waveguides; and first to Mxe2x88x921th rectangular waveguides each inserted between the adjacent circular waveguides, the rectangular waveguides having long sides longer than the diameter of the circular waveguides and short sides shorter than the diameter of the circular waveguides.
Therefore, by appropriately designing the number, spacing, width, height, thickness, and the like of the rectangular waveguides, it is possible to delay a passing phase of a polarization component perpendicular to the wide sides of the rectangular waveguides by 90xc2x0 relative to a passing phase of a polarization component horizontal to the wide sides of the rectangular waveguides. Thus, a linearly polarized wave incident from an input end can be outputted as a circularly polarized wave from an output end.
Furthermore, a passing phase difference between both phases is obtained by delaying the passing phase of the polarization component perpendicular to the wide sides of the rectangular waveguides and at the same time by advancing the passing phase of the polarization component horizontal to the wide sides. Therefore, there is obtained a large phase difference, i.e., 90xc2x0, at a short pipe axis length and thus the circular waveguide polarizer can be reduced in size.
In the circular waveguide polarizer according to the present invention, first to mth circular waveguides may be arranged coaxially and first to mxe2x88x921th rectangular waveguides may be arranged so as to be symmetric with respect to a plane which divides the first to mth circular waveguides right and left into two.
With this arrangement, the circular waveguide polarizer displays improved reflection matching.
According to the present invention, a circular waveguide polarizer comprises: first to mth circular waveguides; and first to Mxe2x88x921th elliptical waveguides each inserted between the adjacent circular waveguides, the first to mxe2x88x921th elliptical waveguides having a major axis longer than the diameter of the circular waveguides and a minor axis shorter than the diameter of the circular waveguides.
Therefore, by appropriately designing the number, spacing, diameter, thickness, and the like of the elliptical waveguides, it is possible to delay a passing phase of a polarization component perpendicular to the major axes of the elliptical waveguides by 90xc2x0 with respect to a polarization component horizontal to the major axes of the elliptical waveguides. Thus, a linearly polarized wave incident from an input end can be outputted as a circularly polarized wave from an output end.
Furthermore, a passing phase difference is obtained by delaying the passing phase of the polarization component perpendicular to the major axes of the elliptical waveguides and by advancing the passing phase of the polarization component horizontal to the major axes of the elliptical waveguides. Therefore, it is possible to obtain a large phase delay at a short pipe axis length and effect reflection matching in a satisfactory manner. Thus, the circular waveguide polarizer can be reduced in size and can operate with improved characteristics over a wide band.
In the circular waveguide polarizer according to the present invention, first to mth circular waveguides may be arranged coaxially and first to mxe2x88x921th elliptical waveguides may be arranged so as to be symmetrical with respect to a plane which divides the first to mth circular waveguides right and left into two.
With this arrangement, the circular waveguide polarizer can operate in good reflection matching.